000
FXUS65 KTFX 271748
AFDTFX

Area Forecast Discussion
National Weather Service Great Falls MT
1148 AM MDT Sat Apr 27 2024

...Aviation Section Updated...

.SYNOPSIS...

Areas of rain and mountain snow will continue across the area
through tonight as a slow moving weather system moves through.
Warmer and drier air arrives for Sunday, but the active weather
pattern will resume as we head into the start of the work week.

&&

.UPDATE...

Lower elevation rain showers and mountain snow, associated with
passing shortwave energy within a southwesterly flow aloft, will
continue for the remainder of the day into tonight. Accumulating
snow over the southwest, currently confined to areas above 6,500
ft, will trend higher to around 7,000 to 8,000 feet as the day
progresses; however, weak convection this afternoon may cause
temporary fluctuations. The inherited winter weather highlights
were left as is for now and will be reevaluated with the afternoon
package. The biggest adjustment to the forecast was to raise pops
for nearly all locations except for the far eastern portions of
Central/North- central Montana. - RCG

&&

.AVIATION...
1148 AM MDT Sat Apr 27 2024 (27/18Z TAF Period)

Rain, with embedded convective elements, continues to overspread the
Northern Rockies this afternoon as a slow moving upper level
disturbance moves from the Four Corners region to over the Central
High Plains. Best chance for thunderstorm activity exists along and
south of the I-90 corridor late this afternoon/early this evening
near the KEKS terminal, with the main threat being erratic winds and
occasional lightning strikes. MVFR/low-VFR conditions will
predominately prevail beneath most areas of precipitation; however,
some shower activity may bring periods of IFR. Precipitation will
begin to diminish from west to east across most of Central through
North Central Montana generally between 03-09z Sunday, but linger
across Southwest Montana through late Sunday morning. Mountain
obscuration will continue for much of the next 18-24 hours. - Moldan

Refer to weather.gov/zlc for more detailed regional aviation weather
and hazard information.

&&

.PREV DISCUSSION...
/ISSUED 423 AM MDT Sat Apr 27 2024/

Key Points:

-- Cooler temperatures this weekend with rain at lower elevations
 and snow in the mountains.

-- Unsettled weather will continue through next week with periods
 of rain and mountain snow.

Short Term (Today through Sunday):

Rain at lower elevations and mountain snow will continue through
tonight as an upper level trough continues to make its way across
the western CONUS. When looking at snow totals, not much changed
compared to the previous forecast so all the current headlines
have remained the same.

By Sunday, most of the precipitation will be confined to the
mountains with some showers possible at lower elevations south of
a line from Helena to Lewistown. Snow accumulations are expected
to remain light with only the highest elevations, well above pass
level, potentially seeing higher amounts.

Long Term (Monday through next Friday):

A parade of weather systems are going to march across the region
through the start of the week with snow in the mountains and
rain/snow mix at lower elevations. The details of when rain will
transition to snow, particularly along the plains, remains a bit
uncertain at this time. There are stronger signals with this
update that lower elevation locations in central Montana and
closer to the Rocky Mountain front may see some accumulating snow.
However, there is still a lot of variance in the models regarding
exact snow totals and given how warm the ground has been, the
risk for accumulating snow remains generally low at this time.
Locations along the hi-line towards Havre and Chinook have a
higher chance of only seeing rain with this event as temperatures
are expected to be warmer heading east.

The second half of the week will be a little warmer as a ridge
tries to build over the intermountain west. Extended model
guidance maintains a lot of disagreement on what happens to the
ridge. The first possible scenario is a weaker ridge that gets
pushed out sooner as the trough moves onshore from the west which
will shorten the dry period and bring more unsettled weather to
Montana. The second possible scenario involves some ensemble
members holding on to the ridge a little longer which will allow
for a couple days of warmer and drier conditions before the
trough moves in during the weekend. At this point in time there is
too much uncertainty to pin down which scenario will play out but
that will be the next round to watch heading into next weekend.

-thor

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  38  60  39  55 /  80   0   0  60
CTB  36  57  36  54 /  80   0   0  10
HLN  39  62  38  55 /  80  10  10  80
BZN  36  59  35  57 /  90  40  30  90
WYS  32  49  28  47 /  90  60  20  90
DLN  35  56  35  54 /  70  10  10  80
HVR  42  66  38  62 /  60  10   0  30
LWT  38  58  36  56 /  30  10  20  90

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 PM MDT this evening for Elkhorn
and Boulder Mountains-Ruby Mountains and Southern Beaverhead
Mountains.

Winter Storm Warning until 6 PM MDT this evening for Gallatin
and Madison County Mountains and Centennial Mountains-Northwest
Beaverhead County.

&&

$$

http://www.weather.gov/greatfalls